Wire mesh and bone plates as methods of bone fixation have been extensively developed during the past few years. Replacement of damaged bone using metal implants is quite common and the current method of fixation has not changed for a considerable period.
Bone plates have been commonly used to replace fractured and unusable bone, particularly in neurosurgery. These preformed plates can be slightly modified by the surgeon to meet the requirements of a specific patient but, in general, are not alterable. In many instances, over a period of time, the bone grows under the plate; however, the plate remains implanted in the patient. The preformed bone plate is fixed to healthy bone by means of a number of small screws. These are small surgical screws that fit in the plate and hold it against the bone.
Wire mesh was developed to overcome some of the restrictions of bone plates. In many instances, preformed bone plates are impractical and the time necessary for the manufacture of the plate in the required form is prohibitive. Mesh was developed to allow the surgeon to form a plate that conforms to the required bone structure directly in the operating room. Mesh has undergone considerable development in design and materials. However, it is still basically an open structure with a number of fixation holes that can be cut and shaped as required. Most mesh is work-hardened, thus, once formed, it retains the required shape. Like bone plates, wire mesh is fixed to the bone by means of a number of small screws.
The current use of wire mesh for fixation of bone pieces in Reconstructive Surgery, Dentistry, Neurosurgery and Orthopedic Surgery has led to the development of multiple designs of mesh. These meshes are generally made out of a corrosion resistant material such as stainless steel or titanium, and have a multiplicity of holes for fixation to the bone by means of small surgical screws.
These surgical screws are usually small flat-head wood or sheet metal screws and are the primary means of attaching the plates or the mesh to the bone. The threads of the screws are designed for gripping the bone. The head of the screw can have any of a multiplicity of designs ranging from a straight slot, cruciate (Phillips head), hexagonal, or other such design. Due to the nature of the material used for implants, neither the screwdriver nor the screws can be of a magnetic material.
The screws are made of a material electrostatically compatible with the mesh, fit into the holes on the plate or mesh, and hold the plate or mesh against the bone. The plate or mesh is countersunk such that if the screw is attached correctly it will not protrude from the surface of the mesh. For correct contact, the screw, must, of course, be centered and perpendicular to the mesh and/or the plate. This imposes significant strain on the surgeon since he must not only keep track of these small components but must also place them absolutely straight; otherwise, the surface of the implant will not be smooth.
Current practice is to supply the mesh or bone plate in a tray with a multiplicity of screws of different sizes, to be used as required. These screws are generally not self-tapping. The surgeon selects the plate or forms the mesh according to the patient's requirements and then selects the appropriate screws for fixing the implant to the bone. He then drills the appropriate number of holes in the bone and uses a screwdriver to drive the screws into place. However, these screws used for mesh fixation are generally small, in the range of approximately one (1) to four (4) mm in length with a diameter ranging from one (1) to two (2) mm. As such, the screws are very difficult to handle even in a controlled environment. In the operating room, with its critical environment and conditions, requiring tracking of all instruments and quick efficient action, these extremely small screws create difficulties for the surgeon and staff. This creates undue stress on the surgeon who must not only place these extremely small screws into place, but must also not over-torque them during the installation, must maintain accurate alignment with the pre-drilled holes, and, above all, must not lose them in the wound. Since these screws are non-magnetic, if they "fall" into the wound they must be located and removed. If the screws are over-torqued during placement, they can shear, which adds an additional problem of removal of the sheared component from the bone and replacement.
The purpose of the present invention is to facilitate the handling, tracking and installation of these surgical screws onto the wire mesh in the operating room.